How do you create a regular expression for a certain string? And can you do it in the Assertion (precondition part of the code)?
I've been google-ing around but couldn't get anything convincing.
The question is like this:
Add a precondition to the DEPARTMENT (the class that we're working on) creation procedure that ensures that the phone number is valid. There are three possible valid phone number formats. A valid phone number consists of one of:
- eight digits, the first of which is non-zero
- a leading zero, a single non-zero digit area code, and then eight digits, the first of which is non-zero
- a leading ‘+’, followed by a two digit country code, then a single non-zero digit area code, and then eight digits, the first of which is non-zero
Any embedded spaces are to be ignored when validating a phone number.
It is acceptable, but not required, to add a PHONE_NUMBER class to the system as part of solving this problem.